Study Finds ‘Supercookies’ Used Outside U.S.

Most major US wireless carriers are no longer using controversial identifiers that some researchers call “supercookies,” but their use appears to be extensive overseas.

That’s the conclusion of a study by privacy group Access Now, which tested how the technology is being used around the world. Supercookies, formally known as unique identifier headers, are virtually undeletable codes that track mobile users’ browsing habits.